Now that all the extended trailers and sneak peeks are out in the open, we still need Supergirl to kick off the big “Invasion!” crossover this coming Monday. So it is with our first “Medusa” clip, that Thanksgiving dinner gets a very Flash-y entrance at an unexpected moment.

The CW released our first official clip from Monday’s “Medusa”; itself not an official part of the four-way crossover, though the hour will see Barry and Cisco recruiting the Girl of Steel. Even in the clip above, it appears as if uncomfortable dinners are giving way to unexplained breaches, so are Barry and Cisco having trouble crossing over?

So reads the “Medusa” synopsis:

A NIGHT OF CONFESSIONS; THE EPIC SUPERHERO CROSSOVER KICKS OFF TONIGHT — Eliza (guest star Helen Slater) comes to town to celebrate Thanksgiving with her daughters. Alex (Chyler Leigh) decides it’s time to come out to her mother; Kara (Melisa Benoist) is shocked when Eliza suggests Mon-El (Chris Wood) has feelings for her, and Winn (Jeremy Jordan) and James (Mehcad Brooks) consider telling Kara the truth about the Guardian. Meanwhile, CADMUS unleashes a virus that instantly kills any alien in the vicinity so Kara enlists an unexpected ally – Lena Luthor (Katie McGrath). The epic superhero crossover kicks off tonight when Barry Allen (guest star Grant Gustin) and Cisco Ramon (guest star Carlos Valdes) seek Kara’s help with an alien invasion on their Earth.

In the meantime, check out the latest trailers below, and stay tuned for more from the big “Heroes v. Aliens” event on Monday!